Currently, many tools are equipped with strain gauges for measuring the twisting forces applied to the tool. Thereby the user can view the value of the strain gauge to decide the force applied to the tool. Thus the screw can be driven properly without breakage.
In the prior art, strain gauge spanner measures twisting forces, however, the driving end of the spanner is fixed. The diving head is not rotatable or the driving head only rotates within a finite range, not omni-direction. Thus the prior art is not suitable for various operating environments. Thereby the working efficiency is low and thus the users are less willing to buy this kind of spanners.